AAAAAAAAAAHHHHHHHHHH!!!!!!!!
Please! The xp isonly part of the problem: we still have the set trap breaking invisibility...
Good?
Wizards shouldn't be setting traps, without rogue levels and considerable hide/MS to make them better at stealth whilst invisible. Those who are both setting traps are either Rogue/Wizards, who should have trouble due to being thinly spread, and other rogues with invisibility potions, who should be good enough at stealth.
Afaik, it dosen't break stealth (though I have limited experience), it just gives you a check of hide/ms vs spot/listen at a penalty (since silently setting a complicated trap, Eg. placing a bomb in a small pit, laying down a bear trap, etc, is considerably harder than just standing still).
If trap setting didn't cancel invis, every Wizard about would be able focus in set trap a bit (not hard with all their skillpoints) and just run around people setting them happily despite having 0 Hide/Ms. Does that seem fair?
I do think it's fair:
a)
1) Traps are expensive.
2) Traps aren't craftable.
3) Traps are VERY hard to recover.
4) Traps add an annoying weight to our always almost encumbered PC's.
Untill what I could discover, to recover a trap in this server you would need at least a DC check of 30, what means a skill level of 10, what means 10 skill points to wizards, what makes we talking about a level 17 wizard, a level 14 if we are talking about skill focus. (correct-me if I'm wrong).
Crafting traps is impossible, unless you're talking about weak traps, which are useless.
Ok, you can buy. But take a look at the prices. They are prohibitive. And you cannot carry many traps, as they take room in our inventories and add weight.
Besides all this, we would still need the "set trap" skill, another investment.
IMHO, for a wizard, investing in trap skills wouldn't be all that useful: he will have much more succes if invest, for instance, in tumble, discipline, parry, etc.
So, the ghost trap making wizard is not a power build.
b) We have server rules regarding the trap usage. Always informing, hostilizing, etc.
c) Traps are fairly easily avoidable (via search, resistance or reflex saves)
d) When we open a lock, a door, a chest, etc, we are forced to make a Hide and MS check to avoid being noticed, being invisible or not. Failing, however, does not break invisibility.
I see no reason why opening a door, chest, lock should be treated any different from setting a trap.
That's a point, opening doors should break it too. 
Invisibility in NWN is far more powerful than it is in PnP. If Jim the level 40 Druid with maximised Listen is sat around chilling, and Beardhammer the 6-Dex Dwarf in his fullplate, chain boots and tower shield chugs an invisibility potion, Jim won't even notice if Beardhammer runs past with his -18 Move Silently model, yodelling the Dwarven National Anthem.
Further: A wizard can pretty easily get 10 Set Trap. Start with 12 Dex (many wizards do), cast Cats Grace and get 16, then take a background that gives a little bonus to it, and you've got 4 points at level 0. Pick up 2 from gear (iirc, there's a belt to give you trap ability), and you only need to be level 5 to have all 10 ranks you need.
If you REALLY pushed it (skill focus, 14 Dex, two backgrounds, gear), you could have 10 Set Trap as a wizard at level 2.
If you want to set traps and suchlike, then invest heavily in Hide/Move Silently for the payoff. Invisibility is so flawed because it's a wizard trying to be a rogue. A rogue gets all the bonuses for their investment, like trapping and unlocking whilst invisible.
Rogues can't summon demons. 
Thanks a lot to you and to Axel for adressing my questions. I still think there's something wrong with the XP roguish system (and I am confident you will take a quick look).
Regarding this last post, two things:
1) I'd invest heavily in Hide and MS if they weren't already nerfed. See: we nerf Hide and MS, then when we complain about the set traps breaking invisibility, people say that we should search for the nerfed Hide and MS system.
It's frustrating to be unable to sneak past zombies.
And dunno if it is just with me, but even with invisibility options, monsters chase me and notice me around then.
Traps are almost prohibitive in the server, most things are immune to sneak attacks, most things can spot listen fairly well. The way things are, rogues are mostly the class everyone already multiclassed or PRClassed take one or two levels just for skill points.
Rogues are probably the most hard class to play in this server, and are used mostly to give skill points to fighters, or to allow assassins and shadowdancers.
2) Rogues do not summon devils? I'll do my best to do it!!!!
